Cisco Nexus 9000 Series Configuration Manual page 70

Configuration Example: Firewall in Layer 3 Clustering
The following table shows a summary comparison of the impact to the cluster control link (CCL) that occurs
with ECMP versus ITD when the ASA device status changes.
Table 3: ECMP versus ITD - CCL Impact Summary Comparison
ASA Status
Steady State
Single ASA Failure
Single ASA Recovery
ASA Addition
Cisco Nexus 9000 Series NX-OS Intelligent Traffic Director Configuration Guide, Release 9.x
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ITD
Minimal traffic on the CCL and
expected traffic types.
Exact same load distribution
irrespective of the type of line card
and switch.
No additional traffic on the CCL.
ITD offers IP stickiness and
resilient hashing.
Traffic redirection can occur on the
CCL between two ASA devices in
the cluster: the recovered ASA that
receives a bucket and the ASA that
previously serviced that bucket.
Minimal additional traffic on the
CCL.
Configuring ITD
ECMP
Minimal traffic on the CCL if the
same line card type and switch
model is used everywhere.
If differing hardware is used, a
higher level of asymmetry might
occur, causing traffic on the CCL
network. Each hardware has a
different hash function.
Two switches (for example, in a
vPC) might send the same flow to
different ASA devices, causing
CCL traffic.
All flows are rehashed, and
additional traffic redirection occurs
on the CCL. Traffic to all ASA
devices in the cluster might be
affected.
Additional traffic redirection can
occur on the CCL. Traffic to all
ASA devices in the cluster might
be affected.
All flows are rehashed, and
additional traffic redirection occurs
on the CCL. Traffic to all ASA
devices in the cluster might be
affected.